1.Field of the Invention
The invention relates to a device for the analysis of liquids, in particular waste water.
All of the devices for the determination of a biological oxygen requirement which are already known involve the measurement of oxygen consumption in a water specimen. They may be subdivided into devices using laboratory methods and on-line measurement methods. The laboratory methods are standardized and described in DIN 38409 Part 51. They involve a dilution method by which the content of biologically degradable substances in the water specimen is determined in the laboratory within five days.
A fermentation calorimeter, which measures the heat production of metabolic processes, is also known. For that purpose, the heat production of the material undergoing fermentation is compensated by a corresponding cooling. The rate of cooling which is determined is proportional to the metabolic heat production and thus is also proportional to the metabolic activity of the biomass. However, the expenditure on apparatus is high, and corresponding systems are too costly for use as a process measurement system.
Known enzyme thermistors measure the heat which is produced when an immobilized layer of enzymes reacts with an organic substance. That heat is measured, for example, through the use of two absolute temperature sensors which are situated in an inlet or outlet of the reaction vessel containing the immobilized enzymes.
In an additionally known flow system, a flow takes place through an enzyme column, at the end of which the temperature is determined. In that case, a second system having an uncoated column serves as a reference. In that case too, a signal difference of the signals from the two temperature sensors is a measure of the heat of reaction.
The known devices for the analysis of waste water are essentially based on the determination of the biological oxygen requirement. The other components of waste water, which frequently exhibit toxic properties or, as nutrient substances, influence the metabolism in nature, are disregarded in most cases. A further disadvantage of the known devices resides in that the waste water to be investigated has to be branched off through additional lines from tanks of clarifying plants and conducted to those devices, since those devices require a very large number of supplementary systems for their operation and, moreover, are sensitive to meteorological factors, so that they can be set up and operated only within a building.